In terms of production, what does 'change in quantity of output' signify?

The phrase 'change in quantity of output' specifically refers to the adjustments in the amount of goods or services produced as a result of varying factors, one of which is the addition of labor input. When more labor is added to the production process, all else being equal, the quantity of output is likely to increase, illustrating the law of diminishing returns at play in production.

This option effectively captures how a direct increase in labor can lead to an increased effort in production, thereby causing a rise in the total quantity of output produced. While efficiency and cost reduction can relate to output changes, they don't directly encapsulate the concept of output change as a result of increased input. Profitability is also an end result that might be influenced by output changes but does not directly define the immediate relationship of input (like labor) to output.